Distributed Solar through the Optimization of Sub-Transmission - PowerPoint PPT Presentation

CESA Webinar Enabling High Penetrations of Distributed Solar through the Optimization of Sub-Transmission Voltage Regulation March 28, 2019

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www.cesa.org

Mult ltis istate In Init itiativ ive to Develo lop Sola lar r in in Locatio ions th that Provid ide Benefit its to th the Grid id www.cesa.org The Clean Energy States Alliance (CESA) is working with five states and the District of Columbia to identify locations where solar and other DERs could increase the reliability and resilience of the electric grid. 4 Learn more at: www.cesa.org/projects/locational-value-of-distributed-energy-resources

Webinar Speakers Nader Samaan Team Lead (Grid Analytics), Energy Infrastructure Group, Pacific Northwest National Laboratory nader.samaan@pnnl.gov Nate Hausman Project Director, Clean Energy States Alliance (moderator) nate@cleanegroup.org

Enabling High Nader Samaan, PhD, PE (PNNL) Penetration of Distributed PV via Project Team: Prof Alex Huang (UT) Prof. Ning Lu (NCSU) Optimization of Dr. Yazhou Jiang (GE), Subtransmission Dr. Greg Smedley (One Cycle Control) Mr. Brant Werts (Duke Energy) Voltage Regulation Clean Energy States Alliance (CESA) Webinar March 28, 2019

Overview Solutions Challenges Outcomes  Voltage regulation at  Develop a Coordinated Real-time Sub-  High penetration of PV (100% subtransmission impedes solar Transmission Volt-Var Control Tool of substation peak load, penetration. (CReST-VCT): without violating voltage   Regulation devices are autonomous and supervisory requirements)  uncoordinated, unable to cope control via flexible algorithm Allow utilities to meet  independently with system net co-optimization of distribution and ANSI, IEEE, and NERC load changes. subtransmission scales standards.  Develop an Optimal Future Sub-  Planning and operational Transmission Volt-Var Planning Tool support to utilities (OFuST-VPT):  Reduce interconnection  Determine the size and location of approval time and cost. new reactive compensation equipment needed to integrate high penetration of photovoltaic (PV) generation.  Consider the coordination achieved by CReST-VCT. 2 March 28, 2019

Overview Solutions Challenges Outcomes  Voltage regulation at  Develop a Coordinated Real-time Sub-  High penetration of PV (100% subtransmission impedes solar Transmission Volt-Var Control Tool of substation peak load, penetration. (CReST-VCT): without violating voltage   Regulation devices are autonomous and supervisory requirements)  uncoordinated, unable to cope control via flexible algorithm Allow utilities to meet  independently with system net co-optimization of distribution and ANSI, IEEE, and NERC load changes. subtransmission scales standards.  Develop an Optimal Future Sub-  Planning and operational Transmission Volt-Var Planning Tool support to utilities (OFuST-VPT):  Reduce interconnection  Determine the size and location of approval time and cost. new reactive compensation equipment needed to integrate high penetration of photovoltaic (PV) generation.  Consider the coordination achieved by CReST-VCT. 3 March 28, 2019

Overview Solutions Challenges Outcomes  Voltage regulation at  Develop a Coordinated Real-time Sub-  High penetration of PV (100% subtransmission impedes solar Transmission Volt-Var Control Tool of substation peak load, penetration. (CReST-VCT): without violating voltage   Regulation devices are autonomous and supervisory requirements)  uncoordinated, unable to cope control via flexible algorithm Allow utilities to meet  independently with system net co-optimization of distribution and ANSI, IEEE, and NERC load changes. subtransmission scales standards.  Develop an Optimal Future Sub-  Planning and operational Transmission Volt-Var Planning Tool support to utilities (OFuST-VPT):  Reduce interconnection  Determine the size and location of approval time and cost. new reactive compensation equipment needed to integrate high penetration of photovoltaic (PV) generation.  Consider the coordination achieved by CReST-VCT. 4 March 28, 2019

PNNL Study * Showed Volt/Var Regulation Challenge at Subtransmission Level System voltage magnitudes increases almost proportionally Voltage violations Voltage violations when the PV increase linearly with PV outputs increase penetration  Under modest penetration of distributed PVs, controlling Capacitor banks in No nearby areas are still overvoltage becomes a challenge at the subtransmission level. coordination switched on in the PV  Voltage regulation challenges at subtransmission are a barrier to of capacitor case bank high penetration of PVs. Developers of new PV projects target switching interconnection to subtransmission to reduce interconnection cost. *Lu S, NA Samaan, D Meng, FS Chassin, Y Zhang, B Vyakaranam, WM Warwick, JC Fuller, R Diao, TB Nguyen, and C Jin. 2014 . Duke Energy Photovoltaic Integration Study: Carolinas Service Areas . PNNL-23226, Pacific Northwest National 5 Laboratory, Richland, WA. http://www.pnnl.gov/main/publications/external/technical_reports/PNNL-22117.pdf

Substation Voltage Profile Comparisons under High PV Penetration (Low vs. High Load) Voltage profile with PV Low Load Day Under low load condition and Voltage profile with no PV Net load = load – PV high PV penetration, there is a potential for overvoltage problems. High Load Day 6

Project Objectives  Coordinated Real-time Sub- Transmission Volt-Var Control Tool (CReST-VCT)  Optimal Future Sub-Transmission Volt-Var Planning Tool (OFuST-VPT) for short- and long-term planning Key Milestones and Deliverables Year 1 Stand-alone prototype of CReST -VCT Year 2 Simulation demonstration of CReST - VCT and prototype of OFuST -VPT Year 3 Field demonstration of CReST -VCT, industry outreach, final report, and the codes for the two tools 7

Scalability of the Solution: Co-Optimization of Transmission and Distribution Voltage 8

Transmission AC Optimal Power Flow for Reactive Power Optimization  Subject to  Objective function: minimize weighted sum of  AC power flow balance on each bus  load bus voltage deviation from target  power plant scheduled real power, except on value distributed slack  transmission losses  power plant scheduled voltage and reactive power  capacitor bank switching limits  load real and reactive power  curtailment of controllable distributed  distributed solar real power output solar output  use of demand response  bounds on reactive power from distributed solar  Output variables:  reactive power requirements from distributed PV at each substation  reactive power form capacitor banks at different substation  real/reactive power required from demand response  real power curtailment from PV 9

Distribution Volt/Var Optimization Tool (NCSU) 10

Improved PV Inverter Active and Reactive Constraint Model 2 2 P Q + ≤ 1 2 2 P Q max max = Q kP max max k is the improved factor for reactive power constraint, 1.1 for a normal IGBT-based PV inverter  k should be adjusted based on power electronics devices and modulation method.  The P / Q constraint is also dependent on the filter and DC capacitor design.  During nighttime when P = 0, reactive power injection results in additional power losses that might become an economic constraint.  Three different reactive power regulation modes can be provided by the inverter (constant Q , constant Power Factor, and volt-var). We are using constant Q that is obtained from the optimization engine. 11

CReST-VCT Implementation CReST-VCT user interface through Python 5 GDX  RAW or use Python to PSS/E update .sav file) AC OPF for (solve Volt/VAR power 3 (GAMS) flow) GAMS  PSS/E 4 6 2 Feeder model (OpenDSS MATLAB/ and GE GAMS 1 Eq) 12

Duke Energy Generation Dispatch Simulation Approach  Methodology  PNNL is leveraging from previous efforts performing solar integration studies for Duke Energy  Production cost simulations for an entire future year, with and without PV were used  Hourly scheduling of generation resources using GenTrader software  Real-time (5 min) redispatch of peaking and Automatic Generation Control (AGC) units using ESIOS (PNNL tool) 13

Duke Energy Data Collection Transmission Model DEC Tie-lines with surrounding BAs  Start with a 2025 Eastern Interconnection base power flow case; build an island of the DEC transmission system.  Identify all tie-lines for each island.  Use consistent import, export, generation, PV, and load assumptions with generation analysis.  Aggregate distributed PV to the nearest substation on the transmission model.  Run chronological AC power flow for the whole system and for the entire study year (8760 power flow cases). 14